At the onset, the Confederacy needed everything it couldn't steal. Which would have been more important: Muskets, powder and materiel? Trains, rails and truck assemblies? Ships and port improvements?
Although the lack of rails and rolling stock was a disadvantage and contibuted substantially to Confederate defeat, it was just one of the handicaps burdening the Confederacy.
Ole
The essential issue is one of balancing the priority of needs. This is always difficult, controversial, and contradictory.
The Confederacy starts out in the middle of a war of rebellion. They need to at least survive that war, and hopefully to win it. If they don't, any course they chose would be proven a failure.
At the beginning, they desperately need an Army of trained, armed, and equipped men strong enough to hold off whatever force the Union sends against them. That means guns and ammo, etc. for the troops as quickly as possible.
That's fine if the war is going to be a short one, with a battle or two or three, over in 1861. If the war is going to be a long one, lasting two or three or more years, then the need for manufacturing equipment and heavy industry will become much more crucial. Failure to build up the industrial base to support the troops in the field will inevitably lead towards doom in a long war.
OTOH, if you are spending too many resources in 1861 on importing manufacturing equipment, RR iron, locomotives, etc. in preparation for a long war, then you risk losing quickly on the field of battle. You might starve the troops of exactly what they need to stave the Union off and give you the time to develop.
There is no easy course here, and "the South" does not have a government already set up, experienced, and running to plan and execute this build-up. It is essentially unprecedented in American history, and they are starting from scratch, with next to no resources in existing organizations or funds, a shortage of trained manpower/talent, little industrial or transportation infrastructure, and almost no industrial commodities production.
They did well with what they had, almost amazingly well. We can find individual items they might have done better, but every choice comes with a cost (monetary, political, military, or industrial) that gets too little consideration in discussions like these.
Give "the South" five or ten years of peace to build their government and economy before they plunge into a foreign war and maybe they could have started to accomplish the things the pro-South side argues for in industrial development. But that requires an entirely different Confederacy and an entirely different set of leaders than the ones who rushed to war in April of 1861. Make a change that big for a "what-if" and the reasonable conclusion would be that "the South" would never have seceded in the first place.
Tim